Recycling of Cr (VI) from weak alkaline aqueous media using a chitosan/ triethanolamine/Cu (II) composite adsorbent.

A Chitosan/triethanolamine/Cu (Ⅱ) (CTS/TEA/Cu (Ⅱ)) composite adsorbent was prepared and applied to recycle Cr (Ⅵ) from aqueous media in alkaline conditions. To investigate the adsorption behavior, the influence of pH was evaluated via batch experiments, and the prepared adsorbent was characterized by FT-IR, SEM, XRD, and Zeta potential. This adsorbent exhibited high adsorption capacity for Cr (Ⅵ) in a wide pH range (especially above 7), suggesting a possible way to separate Cr (Ⅵ) from other metal cations by adjusting the pH value prior to adsorption. Adsorption kinetic and thermodynamic experiments were conducted to explore the adsorption mechanism. Regeneration studies showed that the adsorbent can be reused for five adsorption-desorption cycles without substantial loss of adsorption capacity. Overall, the CTS/TEA/Cu (Ⅱ) adsorbent exhibits high potential for recyclingCr (Ⅵ) from wastewater.

Adsorption of molybdate on molybdate-imprinted chitosan/triethanolamine gel beads.

Mo (VI)-imprinted chitosan (CTS)/triethanolamine (TEA) gel beads (Mo (VI)-ICTGBs) (ICTGBs=imprinted chitosan triethanolamine gel beads) were prepared by using ion-imprinted technology, in which TEA and molybdate solution were used in coagulation bath. The spectrum of FT-IR implies that bonding are formed between TEA and the primary hydroxyl of CTS, and ion gel reaction happen between CTS and molybdate; XRD patterns also prove the change among CTS, TEA and molybdate. SEM images and N2 adsorption show that the surface area increases obviously after eluting Mo (VI) ions. The adsorption isotherm of Mo (VI)-ICTGBs imply that the adsorption process is according with Freundlich model. Adsorption kinetics suggests that the pseudo-second order adsorption mechanism is predominant for this adsorbent system of Mo (VI)-ICTGBs. The Mo (VI)-ICTGBs show high adsorption capacity and good selectivity for Mo (VI) anions in the coexistence system at pH=6.0. The Mo (VI)-ICTGBs have a good application prospect, because it is with a simple and rapid technique and good durance.